The search for a heat source or generator, that does not produce contaminents or pollutants as a by-product, has led innovators to closed loop heating systems initially, and ultimately to a type of apparatus that is commonly referred to as a friction heater.
The basic principles surrounding this type of an apparatus are a closed loop heating source and a heat exchange process, for transferring the generated heat away from the heat generator.
Most prior art devices employ the same basic structures in their operation, i.e., friction generating surfaces moved relative to one another, and a fluid medium such as air or liquid for heat transfer.
Some of the prior art devices rely on convection for the heat transfer process.
Other prior art devices rely on conduction for the heat transfer process.
Still other prior art devices rely on a combination of convection and conduction for the heat transfer process.
Examples of some of the aforementioned prior art devices may be seen be reference to U.S. Pat. Nos.: 4,388,915; 4,381,762; 4,343,291 and 4,285,329.
While all of the aforementioned devices are adequate for their intended purpose, and function in accordance with the well recognized principles enumerated supra; they are deficient both in the complexity of their design, and in their failure to compensate for the inevitable deterioration and subsequent increased spacing between the friction survaces, which results in the decreased heating capacity of the system in which the apparatus is employed.
For the aforementioned reasons, the prior art devices are extremely expensive to fabricate and maintain, and require frequent replacement of the friction surfaces, when only a relatively small portion of the friction material has been consumed by the heating process.